As shown in FIG. 13, a show lace is used to tighten the two flaps of a shoe and the shoe lace is tightened by several steps which require a lot of time to finish. The same steps are taken in reverse sequence when unfastening the shoe lace if the shoe is to be taken off and then, the shoe lace is fastened again every time the shoe is put on. Obviously, the conventional way to fasten or unfasten the shoe lace is time-consuming and cannot meet requirements of people today. FIG. 14 shows a fastening device 1 that is usually used for fastening two ends of a string of back bags or sport clothes. The device 1 generally includes a body 11 with a close end and an open end form which a flange 111 extends inward so as to limit movement of a push member 13 which has one end inserted in the body 11 form the open end and the other end extends from the open end. A spring 12 is biased between the close end of the body 11 and the push member 13 so that the push member 13 has a tendency to move toward the open end of the body 11. Two holes 112 are defined through a wall of the body 11 and a passage 131 is defined through the push member 13. Two ends of the string 2 extend through the holes 112 and the passage 131. When the holes 112 and the passage 131 are located in alignment with each other by pushing the push member 13 inward the body 11, the string 2 can be freely moved by the user. On the contrary, when releasing the push member 13, the spring 12 pushes the push member 13 and the passage 131 is not in alignment with the holes 112 so that the string 2 is biased by the push member 13 and secured. However, it is noted that the spring 12 cannot provide enough force to firmly position the string 2 which can be forcibly pulled easily, and this is the reason why that the fastening device 1 is not used to fasten shoe lace.
The present invention intends to provide a show lace fastening device wherein the shoe lace can be easily fastened or unfastened by pushing two push members of the fastening device.